In the pursuit for solid oxide fuel cell (SOFC) cathode materials which can perform better at 800 degrees C, perovskite structure materials La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF), and Sm0.5Sr0.5Co0.2Fe0.8O3 (SSCF) are studied. Their electrochemical performance as the cathodes is compared by electrochemical impedance spectroscopy (EIS) at 800 degrees C for 100 h through an AISI 441 interconnect/cathode/yttria-stabilized zirconia (YSZ) electrolyte half-cell structure. SSCF cathode has the smallest polarization resistance and is the most desired cathode at 800 degrees C while BSCF cathode has the largest one. SrCrO4 phase forms on the LSCF and SSCP cathodes near the interconnect, but not on the BSCF cathode. With the spin coating of similar to 3 mu m thick Sm0.2Ce0.8O2 (SDC) block layer on the YSZ electrolyte, the polarization resistances of the three cathode materials all decrease. The SDC layer can effectively decrease the mismatch of the thermal expansion coefficients (TECs) between BSCP and YSZ. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.